1. Field of Invention
This invention relates to a communication system that includes fiber optic and wired media.
2. Description of Related Art
Cable communication systems use optical fibers to transmit information between a head-end and a fiber node and use coaxial cable to transmit information between the fiber node and end-users. With increasing need for greater capacity, current systems are stressed to their limits. Thus, there is need for new technology to increase capabilities of communication between head-ends and end-users.
This invention provides a new architecture for a communication system between head-ends and end-users that expands capacity, simplifies transmission and operation, increases reliability and reduces cost of the communication system. One or more mux-nodes in the new architecture receive communication signals from a head-end and forward the received communication signals to one or more mini-fiber nodes (mFNs). The mFNs provide full duplex communication to the end-users. The head-end may include primary hubs that provide connectivity among all end-users of the communication system. The primary hubs also serve as information sources providing services such as TV broadcast signals. The head-end may also include secondary hubs that perform functions such as optical signal distribution and system recovery.
The head-end may be connected to one or more mux-nodes where each of the mux-nodes are connected to the head-end via a small number of optical fibers (preferably two or four). A mux-node may be connected to one or more mFNs via one or more optical fibers, and each of the mFNs may be connected to one or more end-users via passive wired connections such as coaxial lines. In this way, the number of connections to the head-end may be much smaller than if mFNs are connected directly to the head-end without the mux-node.
The communication between the head-end and the mux-node may include analog and digital signals. Digital signals may include digital base band signals (1s and 0s) as well as digital signals modulated onto radio frequency (RF) sub-carriers (RF digital signals). The analog signals may also include the RF digital signals as well as pure analog signals such as TV broadcast signals.
When the analog and digital signals are received together, the mux-node separates the analog signals from the digital signals. The analog signals may be narrowcast signals that are destined to end-users of selected mFNs, for example. The digital signals may be multiplexed using a multiplexing scheme such as time division multiplexing (TDM). The digital signals destined to specific end-users may be demultiplexed and transmitted to the destined end-users through the mFNs that serve the respective end-users. The narrowcast analog signals for each mFN may be combined with digital signals prior to transmitting to the respective mFNs. Each of the mFNs receives the analog and digital signals, modulates these signals onto appropriate RF bands and transmits the signals to the end-users via the passive wired connection.
Upstream RF signals may be received by the mFNs via the passive wired connections from the end-users. The RF signals may include pure analog and RF digital signals. The mFNs may convert some or all of the upstream RF digital signals into digital base band signals for transmission to the mux-node. Alternatively, the mFNs may transmit the RF digital signals directly to the mux-node and the mux-node may perform the RF digital to digital base band conversion.
The analog and digital upstream signals may be transmitted to the mux-node using either multiple optical fibers or wavelength division multiplexing (WDM), for example. The mux-node may RF combine the analog upstream signals from all the mFNs for transmission to the head-end. The RF combining may be performed by either adding the RF signals received from the mFNs together or by frequency division multiplexing the RF signals. The upstream digital signals are processed by the mux-node. Those signals that are destined to the head-end are multiplexed using TDM, for example, and transmitted to the head-end. The analog signals and the multiplexed digital signals may be transmitted to the head-end using wavelength division multiplexing (WDM) or dense wavelength division multiplexing (DWDM), for example.
The mux-node may receive communication signals from end-users through the mFNs that are destined to other end-users connected to the mFNs being served by the same mux-node. In this situation, the mux-node may route the communication signals among mFNs without forwarding the information to the head-end. In addition, routing functions may be performed in the mFNs also. For example, the mFNs may detect that a communication is destined to one of the end-users also connected to the same mFN and route the communication to the end-user without processing by the respective mux-node. The mFNs may also assist the routing process by labeling or adding information to upstream communications so that routing tasks may be simplified at the mux-node, for example. In this way, communication traffic between the mux-node and the head-end may be reduced with corresponding increase in efficiency.
Reliability is increased because the mux-node reduces the number of optical fibers required to be connected to the head-end. The reliability is further increased because a greater distance is spanned by a smaller number of optical fibers between the head-end and the mux-node than distances spanned by a larger number of optical fibers between the mux-node and the mFNs. The wired connections to the end-users are passive and do not include active devices such as amplifiers and thus reduce power consumption and lengthen mean-time-to-failure (MTTF). The small number of optical fibers to the head-end and the lower power consumption of the wired connections shorten the mean-time-to-repair (MTTR) and reduce cost of the communication system.